Sequntial Write or Randon write?

[Gamer Guy]

If I download games in Steam at 550 MB/s and the SSD disk usage is at 672 MB/s, is this disk usage sequential or random write to the disk? What will happen if I download to a 5400 rpm HDD at the same download speed?

[Eigenvektor]

As far as I know, Steam will pre-allocate the file. If there is a large enough continuous free space on your disk, it'll be a sequential write. If your disk is fragmented, then there will be some seek time in between. On an SSD that should hardly matter, and an HDD there will be some (minor) delay. It would only approach a "random write" if your disk was very heavily fragmented.

 

Since no HDD I know of can sustain a write of 672 MB/s, your download would slow down accordingly. I doubt Windows would buffer the whole file in memory until it can be written.

 

~edit: Since Windows is a multi-tasking OS, other processes are probably going to read from or write to disk during your download at some point. So there will most likely be some seek time, whether the file is continuous or not. There is no true "sequential write" in such an environment, since Steam does not have exclusive access to the drive.

[LogicalDrm]

-> Moved to Storage Devices